Ozone producing system

ABSTRACT

According to the system by the present invention, multiple numbers of grooves  13  are formed on the internal surface of said anode compartment frame  6  and said cathode compartment frame  12,  an anolyte gas-liquid separation tower  4  to separate anolyte from ozone-containing gas generated from said anode compartment  1,  being connected to said anode compartment  1  and a catholyte gas-liquid separation tower  5  to separate catholyte from hydrogen gas generated from said cathode compartment  2,  being connected to said cathode compartment  2  are installed outside of said electrolytic cell  3  for ozone producing; achieving enhanced cooling effect of anolyte and catholyte and producing ozone gas at a high efficiency.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an ozone producing system which can achieveprolonged lives of various members composing an electrolytic cell, andcan produce ozone gas at a higher efficiency, as well, by loweringtemperatures inside the electrolytic cell when producing ozone gas bywater electrolysis.

2. Description of the Related Art

The methods to produce ozone gas by means of water electrolysis arepublicly known, where the applied electrolytic temperature is commonlyaround 30 degrees Celsius in order to manufacturing high concentrationozone gas at a high electric current efficiency.

However, electrolytic cells used for ozone gas generation are heated byelectrolysis to a temperature substantially in excess of 30 degreesCelsius and therefore, the internal temperature must be lowered bycooling the electrolytic cells. As a cooling method of electrolyticcells, such methods are known that as shown in FIG. 4, for instance, thetemperature is lowered by heat release from the circulation line throughwhich anolyte is circulated between the anode compartment 1 of theelectrolytic cell 3 and the anolyte gas-liquid separation tower 4, orthe temperature of the electrolytic cell 3 is lowered by proving coolingjackets (not illustrated) on the externals of the anode compartment 2and the cathode compartment 1 composing the electrolytic cell 3. (JP11-315389 A)

However, the system disclosed by JP 11-315389 A demonstratedinsufficient temperature lowering; it enabled to suppress temperaturerise inside the anode compartment and lower the electrolytic celltemperature, but still allowed a high temperature to remain due to thelack of cathode cooling and thus showed inadequate temperature loweringinside the electrolytic cell, especially at the interfaces between theion exchange membrane and the anode, and the ion exchange membrane andthe cathode, where electrolytic reaction is being performed. Because ofthese reasons, uneven temperature distribution occurs inside theelectrolytic cell, causing deterioration of structural members, leadingto lowered ozone gas concentrations or electric current efficiency withtime lapse and eventually resulting in necessity for frequentreplacement of structural members to maintain satisfactory performance.

SUMMARY OF THE INVENTION

Therefore, the object of the present invention is to solve the problemsof said conventional methods, by enhancing cooling effect, suppressingtemperature rise in the electrolytic cell caused by heat generationduring electrolysis, and further, maintaining uniform temperature in theelectrolytic cells at the time when ozone gas is produced by waterelectrolysis, so as to obtain ozone gas at a high efficiency and toprolong various members composing the electrolytic cells.

In order to solve said problems, the present invention constitutes anozone producing system, comprising a perfluorocarbon polymer ionexchange membrane 9, an anode 8 supported with ozone generation catalyston an electrically conductive porous material and a cathode 10 supportedwith platinum catalyst tightly installed on each side of said ionexchange membrane 9, an anode compartment frame 6 installed on the backface of said anode 8, an anode compartment 1 formed between the internalsurface of said anode compartment frame 6 and the back of said anode 8,a cathode compartment frame 12 installed on the back of said cathode 10via a current collector 11, a cathode compartment 2 formed between theinternal surface of said cathode compartment frame 12 and the back ofsaid current collector 11, and cooling jackets 16, 16 installed so as totightly attach to the external surface of said anode compartment frame 6and said cathode compartment frame 12, characterized in that in an ozoneproducing electrolytic cell 3 for producing ozone gas from pure watersupplied to said anode compartment 1; multiple numbers of grooves 13 areformed on the internal surfaces of said anode compartment frame 6 andsaid cathode compartment frame 12; an anolyte gas-liquid separationtower 4 to separate anolyte from ozone-containing gas generated fromsaid anode compartment 1, being connected to said anode compartment 1and a catholyte gas-liquid separation tower 5 to separate catholyte fromhydrogen gas generated from said cathode compartment 2, being connectedto said cathode compartment 2 are installed outside of said electrolyticcell 3 for ozone producing; achieving enhanced cooling effect of anolyteand catholyte and producing ozone gas at a high efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1] Overall view of the ozone producing system by the presentinvention

[FIG. 2-a] Detailed drawing viewed from the upper part of theelectrolytic cell 3 by the present invention

[FIG. 2-b] Detailed drawing, viewed from the side, of the electrolyticcell 3 by the present invention

[FIG. 3] Detailed drawing of multiple grooves 13 formed on the internalsurface of the anode compartment frame 6 and the cathode compartmentframe 12 by the present invention

[FIG. 4] Drawing of ozone producing system by a conventional system

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS

The following explains the mode of working of the invention. FIG. 1 isthe overall view of the ozone producing system by the present invention,FIG. 2-a is a detailed drawing viewed from the upper part of theelectrolytic cell 3 by the present invention, FIG. 2-b is a detaileddrawing, viewed from the side, of the electrolytic cell 3 by the presentinvention, and FIG. 3 is a detailed drawing of multiple grooves 13formed on the internal surface of the anode compartment frame 6 and thecathode compartment frame 12 by the present invention.

The ozone producing system by the present invention is, as shown in FIG.1, composed of an electrolytic cell 3 which electrolyzes purified waterto generate ozone containing gas and two gas-liquid separation towers 4,5 provided in the upper space of the electrolytic cell 3. One gas-liquidseparation tower is the anolyte gas-liquid separation tower 4 which isconnected to the fluoroplastic piping A which supplies ozone gasbubble-contained water from the anode compartment 1 of the electrolyticcell 3 and the fluoroplastic piping B which return water from theanolyte gas-liquid separation tower 4 to the anode compartment 1, havingthe ozone-contained gas outlet 14. The other gas-liquid separation toweris the catholyte gas-liquid separation tower 5 which is connected to thepiping C which supplies hydrogen bubble-contained water from the cathodecompartment 2 of the electrolytic cell 3 and the piping D which returnswater from the catholyte gas-liquid separation tower 5 to the cathodecompartment 2, having the hydrogen gas outlet 15.

The electrolytic cell 3 comprises, as shown in FIG. 2-a and FIG. 2-b, aperfluorocarbon polymer ion exchange membrane 9, an anode 8 supportedwith ozone generation catalyst on an electrically conductive porousmaterial and a cathode 10 supported with platinum catalyst tightlyinstalled on each side of said ion exchange membrane 9, an anodecompartment frame 6 installed on the back of said anode 8, an anodecompartment 1 formed between the internal surface of said anodecompartment frame 6 and the back of said anode 8, a cathode compartmentframe 12 installed on the back of said cathode 10 via a currentcollector 11, and a cathode compartment 2 formed between the internalsurface of said cathode compartment frame 12 and the back of saidcurrent collector 11. The component 7 is an O-ring and the components16, 16 are the cooling jackets installed so as to tightly attach to theexternal surface of said anode compartment frame 6 and said cathodecompartment frame 12.

Multiple numbers of grooves 13 are plurally formed vertically andhorizontally, as shown in FIG. 3, to increase heat-exchange area for ahigher cooling efficiency. In other words, these multiple numbers ofgrooves 13 attempt at facilitating circulation of each anolyte andcatholyte solution, formable in any shape without restriction, includingradial pattern or others.

According to the present invention, purified gas supplied into the anodecompartment 1 of the electrolytic cell 3 is electrolyzed to produceozone-contained gas, which is sent to the anolyte gas-liquid separationtower 4 together with anolyte via the piping A and is separated into gasand liquid in the anolyte gas-liquid separation tower 4, from whichozone-contained gas is vented from the ozone-contained gas outlet 14 andanolyte is circulated to the anode compartment 1 via the piping B.

On the other hand, hydrogen gas generated in the cathode compartment 2is supplied, together with catholyte, via the piping C to the catholytegas-liquid separation tower 5, where separated into gas and liquid inthe catholyte gas-liquid separation tower 5, from which hydrogen gas isvented through the hydrogen gas outlet 15 and catholyte is circulated tothe cathode compartment 2 via the piping D.

According to the present invention, anolyte and catholyte are circulatedbetween the anolyte gas-liquid separation tower 4 and the catholytegas-liquid separation tower 5 and the anode compartment 1 and thecathode compartment 2 of the electrolytic cell 3, respectively;therefore, heat is radiated from the piping A, B, C, and D and thegas-liquid separation towers 4 and 5; and thus cooling is promoted,enabling to achieve a higher cooling efficiency of the electrolytic cell3. Besides, multiple numbers of grooves 13 are formed vertically andhorizontally or radially on the internal surfaces of the anodecompartment frame 6 and the cathode compartment frame 12, contributingto increased areas for heat exchange and decreased solution resistanceof electrolyte passage in the electrolytic cell 3, resulting in furtherpromoted catholyte and anolyte circulations by airlift effect.

According to the present invention, a lower temperature is achieved bothin the anode compartment 1 and the cathode compartment 2, compared withthe case in which circulation system is not provided on the cathode sideof the electrolytic cell 3, and also a smaller temperature distributionin the electrolytic cell 3 is achieved. This temperature descendingeffect becomes more significant when electrolysis is carried out at ahigh current density with concomitant large heat generation.

Furthermore, according to the present invention, the cooling jacket 16,16 are provided so as to tightly attach to the external surfaces of theanode compartment frame 6 and the cathode compartment frame 12. Giventhe electrolytic area of the electrolytic cell 3 is constant,electrolysis operation is carried out at a high current density toincrease the amount of ozone gas output, which, however, results inincreased electrolytic heat generation, causing the temperature rise inthe cell, especially at the contact part between ion exchange membranesand electrodes, eventually leading to decreased current efficiency.

According to the present invention, a higher current efficiency can bemaintained by suppressing the temperature rise in the electrolytic cell3 and at the same time, the life of construction members of theelectrolytic cell 3 can be prolonged. Namely, according to the presentinvention, the temperature in the electrolytic cell 3 did not rise; inparticular, the temperature in the vicinity of ion exchange membrane 9,where is electrolytic heat generation part, was lower than the case ofoperation by the conventional system as shown in FIG. 4. In addition,the temperature distribution in the whole electrolytic cell 3 isminimized. When the electrolytic cell 3 is operated at a high currentdensity to obtain a large amount of ozone gas from less areas, moreelectrolytic heat is generated; and in such case, the temperaturedescending effect by the present invention proves quite effective.

The following explain examples of the present invention. The presentinvention, however, is not limited to these examples.

EXAMPLE

As an example of the present invention, electrolysis was conducted at acurrent density 200 A/dm2 using the ozone producing system shown inFIG. 1. In this experiment, the water electrolysis cell for ozoneproduction, shown as 3 in FIG. 1 employed the cell shown in FIG. 2-a andFIG. 2-b. In FIG. 2-a and FIG. 2-b, 8 is the anode supported with ozonegeneration catalyst on the electrically conductive porous material, 9 isa perfluorocarbon sulfuric acid polymer ion exchange membrane, 10 is acathode supported with platinum catalyst. Whereas, 6 is an anodecompartment frame, and 12 is a cathode compartment frame, on whichmultiple numbers of grooves 13 as explained in FIG. 3 are formed.Anolyte and catholyte were circulated between the anode compartment 1and the anolyte gas-liquid separation tower 4, and the cathodecompartment 2 and the catholyte gas-liquid separation tower 5,respectively. The externals of the anode compartment frame 6 and thecathode compartment frame 12 are provided with the cooling jackets 16,16 for cooling.

On the other hand, as a comparative example, electrolysis was conductedat a current density 200 A/dm² using the ozone producing system, asshown in FIG. 4, in which only anolyte was circulated between the anodecompartment 1 and the anolyte gas-liquid separation tower 4, having nocirculation system on the cathode side. In this comparative examplealso, the cooling jackets 16, 16 are provided for cooling the anodecompartment 1 and the cathode compartment 2.

Table 1 shows the results of said example and said comparative example.These results show that the case in which anolyte and catholyte werecirculated between the anode compartment 1 and the anolyte gas-liquidseparation tower 4 and between the cathode compartment 2 and thecatholyte gas-liquid separation tower 5, respectively gives a lowertemperature of the entire cell, a smaller temperature distribution, anda higher current efficiency in terms of ozone production than the casein which only anolyte was circulated between the anode compartment 1 andthe anolyte gas-liquid separation tower 4.

TABLE 1 Catholyte mean Anolyte mean Temperature Temperature Ozone gastemperature temperature Distribution Δ Distribution Δ current (° C.) (°C.) (° C.) (Cathode) (° C.) (Anode) efficiency (%) Example 35 39 7 618.3 Comparative 38 39 10 10 18.0 Example

The ozone producing system by the present invention allows the anodecompartment and the cathode compartment to be cooled by the coolingjacket and also such cooling is further promoted by heat release broughtabout through circulating anolyte and catholyte of the electrolyticcell. Also, the anode compartment and the cathode compartment which havevertically and horizontally or radially formed grooves allow enhancedcirculation of catholyte and anolyte by airlift effect, suppresstemperature rise of the cell by heat generation during electrolysisoperation, achieve ozone gas generation at a high efficiency throughuniform temperature within the electrolytic cell, and prolong lives ofvarious structural members constituting the electrolytic cell.

This application claims the priorities of Japanese Patent Application2006-215500 filed Aug. 8, 2006, the teachings of which are incorporatedherein by reference in their entirety.

1. An ozone producing system, comprising a perfluorocarbon polymer ionexchange membrane (9), an anode (8) supported with ozone generationcatalyst on an electrically conductive porous material and a cathode(10) supported with platinum catalyst tightly installed on each side ofsaid ion exchange membrane (9), an anode compartment frame (6) installedon the back of said anode (8), an anode compartment (1) formed betweenthe internal surface of said anode compartment frame (6) and the back ofsaid anode (8), a cathode compartment frame (12) installed on the backof said cathode (10) via a current collector (11), a cathode compartment(2) formed between the internal surface of said cathode compartmentframe (12) and the back of said current collector (11), and coolingjackets (16, 16) installed so as to tightly attach to the externalsurface of said anode compartment frame (6) and said cathode compartmentframe (12), characterized in that in an ozone producing electrolyticcell (3) for producing ozone gas from pure water supplied to said anodecompartment (1); multiple numbers of grooves (13) are formed on theinternal surfaces of said anode compartment frame (6) and said cathodecompartment frame (12); an anolyte gas-liquid separation tower (4) toseparate anolyte from ozone-containing gas generated from said anodecompartment (1), being connected to said anode compartment (1) and acatholyte gas-liquid separation tower (5) to separate catholyte fromhydrogen gas generated from said cathode compartment (2), beingconnected to said cathode compartment (2) are installed outside saidelectrolytic cell (3) for ozone producing; achieving enhanced coolingeffect of anolyte and catholyte and producing ozone gas at a highefficiency.